Known in the art is an exhaust purification system for an internal combustion engine in which an NOx storage catalyst is arranged in an engine exhaust passage and a hydrocarbon feed valve is arranged upstream of the NOx storage catalyst in the engine exhaust passage and in which rich control which makes an air-fuel ratio of the exhaust gas which is exhausted from a combustion chamber rich is performed to release NOx from the NOx storage catalyst and remove the NOx, and clogging preventing injection which injects hydrocarbons from the hydrocarbon feed valve is performed during the rich control to prevent clogging of the hydrocarbon feed valve (for example, see PLT 1). In this exhaust purification system, clogging preventing injection is performed when the NOx release speed is high during the rich control, that is, in the middle period of rich control. Note that, the NOx storage catalyst of this exhaust purification system contains ceria. Therefore, the NOx storage catalyst has an oxygen storage ability.